Edge welded metal bellows are manufactured by welding stamped, metal diaphragms into a long, flexible assembly. The key to the performance of the edge-welded bellows is the thickness and ripple profile of the metal diaphragms. The pressure, stroke length, spring rate and temperature help to determine the material and the thickness of the diaphragm required to meet the applications demands. The inside and outside edges of the diaphragm and the shape of its ripples are also crucial to the performance of the bellows assembly.
When the ripple profile and the thickness of the diaphragm are determined, the diaphragms are hydraulically stamped from strips of metal in sheet form. Once stamped, diaphragms are inspected for quality and cleaned. The cleaning preparation varies between manufacturers, but the main focus is to ensure that the material is free of any grease or dirt to ensure the welds are strong and leak-tight. The diaphragms need special handling after the cleaning process as well, to ensure that the natural oils of skin do not come into contact with the diaphragms. The diaphragms are positioned back-to-back to pair the inside diameter holes. Once the inside diameters come into contact with each other, they are welded together. Depending on the manufacturer and material, welding can be accomplished through plasma, laser, arc, or electron beam welding equipment. Vision systems can aid the accuracy and consistency of welds. This process is continued in order to make the proper number of convolutions. The convolutions give the bellows assembly the flexibility and performance characteristics.
Once the inside diameter welds are completed, the outside diameter convolutions can be prepared for welding. Depending on the welding equipment, copper rings can be inserted between the convolutions in order to ensure that the heat from the welds do not distort or change material properties in the adjacent material. End plates or flanges can be welded to the end of each side of the bellows assembly per customer requirements. Once completely assembled, edge welded bellows are helium leak tested to ensure the assembly is completely sealed. The industry standard leak rate is 1×10E-9 for stainless steel material, but lower leak rates are required for certain applications.
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